Nuclear reactors typically include control rods containing materials for neutron absorption and for either shutting down or shaping nuclear reactions. Conventional control rods (or control blades) in Boiling Water Reactors (BWR), have a cruciform shape and pass in complementary cruciform shaped interstices (called fuel channel gaps) between fuel assembles of fuel rods.
Prior art control rods consist of a plurality of elongated members, configured side-by-side to form a planar member. These elongated members, known as absorber tubes, are sealed at both ends and may contain capsules containing boron carbide powder, or other neutron absorbing materials such as hafnium rods.
Four planar members, each consisting of a plurality of absorber tubes, are welded to a central generally cruciform member, to form a cruciform shaped control rod.
U.S. Pat. Nos. 4,929,412 and 4,902,470 disclose a control rod 100 including an absorber tube T with four discrete right angle corners. As shown in FIG. 1, adjacent absorber tubes T are welded together at corners 10, where reference numeral 20 indicates welded material between adjacent absorber tubes.
FIG. 2 is a perspective view illustrating a control rod, coming up from under four side-by-side fuel channels, for absorbing neutrons in the control of a nuclear reaction. FIG. 2 illustrates how fuel assemblies are arranged around control rods on a BWR. The nuclear reactors have fuel channels 14 containing fuel rods 16. Interior of the fuel rods 16 are placed the nuclear fuel pellets which generate the chain nuclear reaction. BWR type reactors introduce the control rods from the bottom towards the top. Such a control rod R is shown in FIG. 2 coming up between the respective fuel channels 14 separating fuel assemblies of fuel rods 16.